I was wondering why the Premium Citadel Tiger has the tracks on the lower plate count as spaced armour, yet the 131, Hammer and Tiger 1 ( Tech Tree) do not have this placed armour though visually look the same?

The Japanese Heavy tank #6 does not have the piece of track there so understandably does not have any added placed armour.

Why is it that the Citadel is the only variant of Tiger with spaced armour? especially at tier VI!

Citadel has 950 HP, so it's kinda nice to have at least some additional armor. On the other hand, Jap Tiger also has 950 health, but no spaced armor. I guess Germans sold whole tank in parts except that slapped on piece of tracks on lfp. Japs should've payed a couple of mil extra for that.

The 13. (Tiger) Kompanie, of Panzer Regiment Großdeutschland, reported on the performance of the 88 mm KwK 36 L/56, when their Tigers engaged the T-34: "First round hits were usually achieved at ranges between 800 to 1,000 meters. At these ranges, the Panzer Granate (they are referring to the PzGr. 39 APCBC ammunition) absolutely penetrated through the frontal armor, and usually still destroyed the engine at the rear of the T-34 tank. In 80 percent of the cases, shots from the same range hitting the side of the hull toward the rear of the tank resulted in the fuel tanks exploding. Even at ranges of 1,500 meters and longer, during favorable weather, it is possible to succeed in penetrating the T-34 with minimal expenditure of ammunition" (JENTZ, Thomas L.; Germany's TIGER Tanks - Tiger I and II: Combat Tactics; op. cit.).